1. Field of the Invention
The present invention relates to a multilayer ceramic electronic component and a method for manufacturing the multilayer ceramic electronic component. Particularly, the present invention relates to a multilayer ceramic electronic component in which an external terminal electrode connected to an inner conductor is formed on the surface of a ceramic body by direct plating and a method for manufacturing the multilayer ceramic electronic component.
2. Description of the Related Art
In recent years, the market for small portable electronic devices such as cellular phones, notebook computers, digital cameras, and digital audio devices has expanded. Portable electronic devices with not only smaller sizes but also higher performance have been rapidly developed. Such portable electronic devices include many multilayer ceramic electronic components. For such multilayer ceramic electronic components, smaller sizes and higher performance are also required. For example, multilayer ceramic capacitors with smaller sizes and larger capacitances are required.
To achieve multilayer ceramic capacitors with smaller sizes and larger capacitances, it is effective to make ceramic layers thin. Capacitors whose ceramic layers have a thickness of about 3 μm or less have been used recently. At present, much thinner layers are required. However, a short circuit between internal electrodes is more likely to occur as the thickness of ceramic layers decreases. This causes problems with quality assurance.
To achieve multilayer ceramic capacitors with smaller sizes and larger capacitances in a different manner, it is effective to increase the effective area of the inner electrodes. When multilayer ceramic capacitors are mass-produced, the side margins between an inner electrode and the side surface of a ceramic body and the end margins between an inner electrode and the end surface of a ceramic body must be ensured to some extent, due to displacement that may occur during stacking or cutting ceramic green sheets. Therefore, when the effective area of the inner electrodes is increased, the area of the ceramic layers must be increased to ensure a margin. However, increasing the area of ceramic layers within the predetermined size standards of products has its limit, and the thickness of external terminal electrodes prevents the area of ceramic layers from being widened.
The external terminal electrode of multilayer ceramic capacitors has been formed by applying a conductive paste to the end of a ceramic body and baking the conductive paste. The primary method for applying a conductive paste is to immerse the end of a ceramic body in a paste tank and then pull the ceramic body out of the paste tank. However, a thick conductive paste easily adheres to the central portion of the end of the ceramic body with this method due to viscosity of the conductive paste. Thus, a portion of the external terminal electrode is thick (specifically more than about 30 μm), and the area of ceramic layers must to be decreased by the thickness of the external terminal electrode.
Accordingly, a method for forming an external terminal electrode by direct plating has been proposed. In this method, a plating film is deposited at the exposed portions of the inner electrodes on the end surface of a ceramic body, and the plating film grows. As a result, the exposed portions of the inner electrodes that are adjacent to each other are connected. According to this method, a thin flat electrode film can be formed as compared to the existing method that uses a conductive paste (See WO 2007/049456).
Although the high bonding strength of an external terminal electrode to a ceramic body due to an adhesive effect of glass is achieved in the existing method for applying a conductive paste and baking it, such high bonding strength cannot be achieved in the method for forming an external terminal electrode by direct plating. Therefore, the bonding strength of an external terminal electrode defined by a plating film to a ceramic body tends to be insufficient, which causes a problem of low reliability.